Removing Field.to_write and FieldSet.to_write methods #749

Job	Run time
mypy	3m 38s
py3.13 \| macos \| integration tests	18m 10s
py3.13 \| macos \| unit tests	5m 5s
py3.13 \| ubuntu \| integration tests	14m 47s
py3.13 \| ubuntu \| unit tests	5m 34s
py3.13 \| windows \| integration tests	26m 40s
py3.13 \| windows \| unit tests	15m 30s
py3.10 \| ubuntu \| integration tests	14m 56s
py3.10 \| ubuntu \| unit tests	5m 33s
py3.11 \| ubuntu \| unit tests	5m 39s
py3.12 \| ubuntu \| unit tests	5m 59s
merge-test-artifacts	0s
	2h 1m 31s

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